[FR] add disconnect command in isql

[basid-irk]

Currently no way close connection without leave isql - only exit and quit command exist. Will usefull add disconnect command with parameters:

• commit [transaction]
• rollback [trasaction]
• [no ]reset [settings]

with "no reset commit" as default.

[aafemt]

ISQL without connection is useless. Establishing a new connection automatically close the old one.

[asfernandes]

It may make sense as isql has shell command which may work with the local file after it's disconnected inside a script.